Signal says a contact's safety number changed: verify before a sensitive message

Signal creates a unique safety number for each one-to-one conversation. A change can follow a new phone or reinstall, but an unexpected change also warrants a pause before sending sensitive material. The number helps verify the encrypted connection; it does not independently prove a stranger is who they claim to be.

Before you start​

Choose a separate contact route already known to belong to the person, such as an established call or in-person meeting. Avoid using only the same Signal conversation to ask whether it is safe.

Do it step by step​

1. Open the relevant Signal chat and read the safety-number change notice. Do not approve or send a sensitive document reflexively.
2. Contact the person through the independent route and ask whether they switched phones or reinstalled Signal. Confirm the circumstances, not just a yes/no answer.
3. Have both parties open the chat's View Safety Number screen. Compare the full numeric value or scan the QR code in person where possible.
4. When the values match and identity is established by the separate channel, mark the number as verified on your device if the conversation warrants it.
5. If values differ or the person's story does not match, stop sharing sensitive content and investigate account or device access before continuing.

Check the result​

Both sides should see the matching safety number for the current conversation. Marked verification should persist until the number changes or you clear it.

If something goes wrong​

A contact may legitimately change phones without warning. An undelivered message sent under an older safety number may not be resent automatically; confirm delivery after the check.

Know the limit​

A matching safety number authenticates the encrypted channel relative to what was compared. It is strongest when the comparison happened through a separately trusted path. Signal safety-number instructions